Rainbows/Transcript
Transcript Old Version Text reads: The Mysteries of Life with Tim and Moby Tim reads from the typed letter. TIM: Dear Tim and Moby, what's really at the end of a rainbow? From, Roy. New Version Text reads: The Mysteries of Life with Tim and Moby Tim and Moby are sitting at a picnic table in their backyard. MOBY: Beep. Beep. Beep. Moby holds his hands up. TIM: For the last time, there's no such thing as– MOBY: Beep. Moby holds up a unicorn's horn that has a rolled up letter inside of it. TIM: Yes, I know about their horns. Tim reads from the typed letter. TIM: Dear Tim and Moby, why can't I ever get to the end of a rainbow? Thanks, Roy. Hey, Roy. The simple answer is that rainbows are optical illusions. That's when light plays tricks on our eyes. What we see as a colored band stretching across the sky, is really just sunlight bouncing off of millions of raindrops. An image shows a rainbow in the sky and rainbow colors bouncing off of raindrops. MOBY: Beep. TIM: Well, the sun produces a few different types of light. We divide them up based on their wavelengths. A chart shows three different kinds of lights and their wavelengths: ultraviolet light, visible light, and infrared light. MOBY: Beep? TIM: That's the distance between the tops of a wave. An image shows a wavelength as the distance between the top part of two waves. TIM: Infrared and ultraviolet wavelengths are invisible to us. These two wavelengths disappear from the chart. Visible light and its wavelength remain. MOBY: Beep? TIM: To humans, anyway. People can see the wavelengths that make up visible light. All mixed together they appear white. But white light contains a whole range, or spectrum, of wavelengths. When they're split apart, our eyes register them as different colors. Visible light is shown as white. It splits into rows showing all of the colors of the rainbow and their unique wavelengths. MOBY: Beep? TIM: Well, every type of animal perceives their own unique spectrum. Some creatures can even see ultraviolet and infrared light. An image shows that birds can see ultraviolet, visible, and infrared light. TIM: Others can pick up finer shades of the same colors we see. An image shows a butterfly and a caterpillar on a background of gradients of primary colors. MOBY: Beep? TIM: Our friend Sadie barely recognizes more than two hues. An image shows Sadie and shades of blue and yellow. TIM: And human vision breaks visible light into seven major colors. Look familiar? An image shows the seven colors visible to humans: violet, indigo, blue, green, yellow, orange, and red. MOBY: Beep. TIM: Yup. They're the same colors we see in a rainbow. I'd explain why but I need some raindrop– Moby is spraying water from a hose. TIM: That'll work. As light from the sun hits a raindrop, it slows down. The change in speed shifts its direction a tiny bit. The light is being refracted, bending as it travels from one material to another. An animation shows light bending as it enters a raindrop. MOBY: Beep? TIM: Remember, white light contains a number of wavelengths. They each slow down a different amount inside a raindrop. That makes them bend at slightly different angles, getting farther and farther apart as they move. This is called dispersion. The beams of light reflect off the other side of the water droplet. An animation shows white light splitting into the rainbow colors inside a water droplet. The animation shows the different speeds and angles of the light inside a raindrop. The colors of the rainbow bend and move apart and reflect off the side of the raindrop. MOBY: Beep? TIM: Think of the drops like tiny curved windows. Some light passes through, but some gets reflected back. Moby waves at his reflection lovingly while looking at a window. TIM: Are you done? Can we move on? MOBY: Beep. TIM: As the dispersed sunlight leaves the drop, it refracts again, further separating the colors. Imagine millions of raindrops doing this at the same time. An image shows the dispersed sunlight as rainbow colors projecting from the water droplet and moving farther apart. The image expands to show mant water droplets projecting rainbow colors. MOBY: Beep. The water spraying out of Moby's hose reveals its rainbow colors. TIM: Yep, full rainbows only appear under special conditions. Like when the sun peeks out while it's raining. You have to be between the sun and the rain, with your back to the sun. An animation shows Moby facing a rainbow in a rainstorm with his back to the sun. TIM: From there, it's all about the angles. The sun needs to be pretty low compared to where you're standing. If it climbs above a certain height, the rainbow disappears. The animation shows the sun moving up and the rainbow disappearing from view. MOBY: Beep? TIM: Think of it like the sun drawing a circle on a sheet of rain. The part we can see changes with the sun's movement across the sky. We can see more of the circle in the morning and evening. And less of it closer to midday. An animation shows Moby viewing the rain sheet from an angle. A white circle is drawn between him and the rain. The top part of the circle appears as rainbow colors. As the sun moves, the amount of the circle visible to Moby changes as Tim describes. MOBY: Beep? TIM: We rarely see the lower half of a rainbow because the ground gets in the way. If you're really high, like above a waterfall, you might see a fuller circle. Moby is shown on top of a cliff viewing a full rainbow that encircles a waterfall. TIM: The lower half is created by the water droplets below you. A pop-up image details the light dispersion in the water droplets. A unicorn appears on the cliff opposite Moby. MOBY: Beep? TIM: Nope, it's not any easier to reach the end of larger rainbows. Move forward and you'll see an identical rainbow. It's just bouncing off a sheet of rain that's a bit farther away. Move to the side, and the rainbow moves with you. The animation shows Moby viewing the rainbow with the sun at his back. As Moby walks toward the rainbow, it does not change. When Moby moves to the side, the rainbow moves along with him. TIM: It's like trying to get away from your own shadow. Speaking of which, your shadow always points to the center of the rainbow. The rainbow is shown on the top half of the circle from the previous animation. A dot is placed at the center of the circle. An arrow shows Moby's shadow points toward the dot. TIM: Pretty cool, huh? MOBY: Beep? TIM: Sure, yes. If unicorns existed, then maybe you could get... Tim hears large wing flaps, looks up, and sees Moby riding a unicorn. MOBY: Beep. Beep. Moby's beeps fade as he soars up towards the rainbow on the unicorn's back. TIM: Uh, you didn't see that! Tim puts his hands up to block the camera. Category:BrainPOP Transcripts Category:BrainPOP Science Transcripts